Processes and devices for moving injection units are generally known. The plastic granules plastified in the injection unit, after they have reached the flowability necessary for injection and temperature necessary for it, are injected into the closed mold at high speed and for this reason also at high pressure. It is therefore necessary to press the nozzle, part of the injection unit, firmly against the mold, so that the plastified plastic composition cannot escape between the nozzle and mold.
In order to increase the contact forces in a hydraulic press, German 295 04 297, proposes to immerse a piston of smaller diameter into the cavity of a larger working cylinder filled with a fluid. The fluid displaced in this manner increases the pressure in the working cylinder and consequently the contact force produced by the working cylinder.